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**1 - 2**of**2**### On Some Aspects Of Insertion Languages

, 2007

"... iii Insertion grammars, introduced in 1981 by Galiukschov, can generate languages which can incorporate limited amount of context sensitive information in their deriva-tions. Production rules in such a grammar consist of rewriting of the form uv → uxv, i.e., the string x can be inserted in the conte ..."

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iii Insertion grammars, introduced in 1981 by Galiukschov, can generate languages which can incorporate limited amount of context sensitive information in their deriva-tions. Production rules in such a grammar consist of rewriting of the form uv → uxv, i.e., the string x can be inserted in the context (u, v). Rewritings of this kind can model various natural situations, e.g., in linguistics, as well as in molecular biology. We present here in this thesis a polynomial time parsing algorithm for insertion lan-guages, a problem which was open till date. Our algorithm can also be simply modified to parse internal contextual languages in polynomial time. Besides this general parsing algorithm, we also provide efficient and simple parsing algorithms for two subclasses of insertion languages. Our thesis also considers some closure properties of the class of insertion languages, the results of which point out the difference of this class from the class of context free languages. iv Dedicated to